The Low Emission Zone (LEZ) was introduced on 4 February 2008, with a phased introduction through to January 2012. The aim of LEZ is to improve air quality in London by deterring the most polluting vehicles from being driven in the area. Affected vehicles include older, diesel-engined lorries, buses, coaches, large vans, minibuses and other heavy vehicles that are derived from lorries and vans, such as motor caravans and motorised horse boxes. Different vehicles will be affected over time and increasingly tougher emissions standards will apply. Cars, motorcycles and small vans will not be affected.